Mine too. But I think the US failures were related to high millage Leafs (Leaves?) in hot climates and that they've improved the design since it was launched.
True, heat does play its part as they didn't include active cooling. In California there are quite a few reports of Leafs whose maximum range dropped below 60 miles after 5 years. They've changed the battery chemistry since the early generation ones to be more heal tolerant, but there's still a way to go there.
While the modules can be replaced independently, and there are some specialists in the UK who will do this for less than Nissan charge (I assume as I've yet to see official Nissan pricing), that's only effective for cell failure rather than degradation that affects all cells.